The major objective of this project is to develop a guinea pig model of CMV infection that simulates CMV infection in the compromised human host. Guinea pigs are being treated with several immunosuppressive agents beginning at the time of CMV inoculation as well as after the establishment of chronic persistent infection. Virus titers in various body compartments and histological evidence of CMV infection are being examined. In addition, the effect of CMV infection in cellular immune response both in vitro and in vivo is being investigated with particular attention to the effect of CMV infection on pulmonary host defense mechanism.